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Comparison between Galvanic and Electrolytic Cell

Mr Khemistry

Comparison between galvanic and electrolytic cell table

Students tend to get mixed up between the two types of electrochemical cells. This table will illustrate the comparison between galvanic and electrolytic cell.

A useful acronym, P.A.N.I.C. for electrolytic cell polarity (Positive is Anode Negative is Cathode). Then just remember polarity is reversed for galvanic cell.

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Physical Chemistry Calculations – Be Aware Where Errors Occur

Mr Khemistry

Physical Chemistry Calculations

Physical Chemistry – Recently i was revising acid-base equilibrium with one of my students and i realised she has trouble getting the right answer even though the procedure is correct. We went through the process and every step was conceptually correct. Then i got her to show me how she calculated on her GC, i saw the workings and it was right. But when she pressed “=”, the answer came out wrong!

Boy, was i puzzled. We went through the steps carefully again and still we arrived at the same outcome. Finally, after i queried her on one of the steps, we both realised what’s wrong. She did not use brackets to sequence the operations, thus the calculator did not process the workings in the sequence we wanted.

A few more questions with calculations we encountered different problems, like missing out a zero or misreading a digit. I pointed out to her none of the questions we did had any mistakes conceptually, only the numerical answers were wrong. I asked her would she be discouraged and come to the conclusion physical chemistry is difficult? She said yes. And no wonder, after thinking so hard and so many calculations, the final answer always turned out to be wrong.

I taught her to carefully check through her workings when doing calculations and look out for common errors. Most importantly, not to be discouraged and come to the wrong conclusion physical chemistry is hard! Most of the calculations in physical chemistry is NOT hard, we just need to practise and look out for common errors.

Do you find physical chemistry daunting? You can do well in it!

Come join us at our weekly group tuition to see how you can confidently approach calculations too!

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Chemistry Tuition by Mr Eric Kua

Mr Khemistry

Chemistry Tuition by Mr Khemistry

Looking for a good, reliable Chemistry Tuition? We understand there are many centers that offers Chemistry Tuition nowadays and it’s difficult to tell which ones are worth your time. Here we compile a list of reasons why Mr Khemistry is the Chemistry Tuition you are looking for.

  1. We are Qualified. Our Principal Tutor, Mr Eric Kua, graduated from NUS with a Degree majoring in Chemistry. He has taught in a JC for more than 8 years. For his full academic and teaching qualifications, click here.
  2. We are Experienced. All our tutors have over 10 years of experience tutoring students in Chemistry, Mr Eric Kua has more than 13 years of experience in Chemistry tuition.
  3. We are Committed. Our goal is the same as yours, to unlock the potential that is in every student. We offer unlimited consultations via whatsapp and revision crash courses during holiday period to bring every student up to speed.
  4. We are Specialists. Our focus on Chemistry allows us to hone our pedagogy in this subject to a much greater depth. Think about why we visit specialists in hospitals. Yup.
  5.  We are Accessible. Our locations are conveniently located within walking distance from MRT stations (Beauty World and Bishan).

Pre-qualification

After many years of tutoring students from different ability levels, there is some common characteristics of students who are likely to benefit from attending group lessons with us. Here are some for your consideration.

  • They are consistent. They do not skip lessons to attend birthday parties. If they have important appointments that clashes, they will endeavor to go to another class for make-up lesson.
  • They are willing to put in effort after lesson to revise their work. We give additional practise for the students, those who improve dramatically are usually the ones who take the time to attempt these extra practise and consult the tutor when they are unsure.
  • They do not attend more than two tuition every week. Attending more than two tuition lessons every week saps their energy and takes away revision time. More likely they are using it as a clutch rather than a real need.
  • They reflect and THINK about what are the main concepts after lessons. Students who simply take everything at face value without thinking, memorizing their notes, are unlikely to excel in Chemistry at A levels. A simple test would be to look at their summarized notes, a student who has thought through would organize his/her notes quite differently from one who merely copy and paste from lecture notes.

Remember, it takes two hands to clap. You can engage the best Chemistry tutor but if you do not do your part, the results are unlikely to change. We will provide concise illustrated notes with clear teaching, putting the best resources at your disposal, what you do with it will determine the outcome.

Born Haber Level Diagram

Mr Khemistry

Born Haber Level Diagram

Born Haber Level Diagram

Always start your cycle at datum line, i.e. at zero enthalpy. Tip: You may combine the ionisation energies for Fe or for other metals.
Multiple electron affinities can also be combined.

Take note that for energy level diagram, you will have to show the ionized electrons from Fe. When you use bond energy instead of enthalpy of atomisation, you will need to multiply by the correct coefficient. Lastly, don’t forget to put your state symbols! 🙂

Hope this has been useful for you, if you wish to learn how to draw the diagram using energy cycle, go here.

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Born Haber Cycle

Mr Khemistry

Born Haber Cycle

Born Haber Cycle Diagram

Born Haber Cycle

Using the acronym F.A.I.L. where F stands for enthalpy change of formation of the ionic compound, A stands for atomisation of the constituent elements and I stands for ionisation of cation and anion and L stands for Lattice Energy.

We have four major components  and this energy cycle is easy to draw with no worries about which species having a higher energy level. There is no need to include electrons as they are immediately used to form the anion.

Hope this has been useful to you! Share it with your friends if it has helped you 🙂

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JC Chemistry Tuition in Bishan

Mr Khemistry

JC Chemistry Tuition in Bishan

We will be starting classes at Bishan this June, on Monday and Friday evenings. For a start, there will be one JC2 class and one JC1 class. Went down to the area to take a professional photoshoot and it was quite good. 

JC Chemistry Tuition in Bishan

Our tuition centre is located within walking distance from the Bishan bus interchange. Do check out our class schedule if you are interested to sign up for H2 Chemistry Tuition.

PS: We have started classes at Bishan, with J1 classes every Monday and J2 classes every Friday. Check our class listings to keep up with updates to the class schedule!

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Organic Novel Questions Book

Mr Khemistry

Organic Novel Questions Book

Novel Organic Questions Book

By the time this post is published, hopefully we would have finished the proofreading and sent for printing. Distribution to the bookstores might take a month or so but i hope to make it in time for the 2019 A levels Examination. This is my second book and i hope it will cater to a different group of students. If you recall, my first book was to meet the demand from private candidates who needed practical worksheets for practice. This Organic Novel Questions Book hopes to address the needs of students who are competent doing the standard questions and want to stretch themselves. 

This doesn’t mean that average students shouldn’t buy the book. It only means they shouldn’t buy it to use as a guide book. This is like the apex of organic chemistry, students need to be familiar with the basics first. 

I already have parents and students asking when will the book be out, i can only hope soon. Hopefully students will find it a useful tool to sharpen their critical thinking. Instead of giving thousands of questions, i have chosen to select 30 of the most challenging ones. It is my belief that quality thinking is far more important than rote learning. Of course practising basic standard questions is a given but once passed that stage, students should not be looking for repetition. 

Side note on Organic Novel Questions Book

Just a note though, do not be disappointed even if you can’t do any of these questions (some of these reactions are only taught in University Level 1 modules). It is very likely none of these questions will come out in A levels! What i hope for is that it shows you how we can think about such novel questions. Obviously this thinking process is different for everyone, i’m just showing you a few ways to approach such questions. 

One last word, if you found the book useful, please recommend it to your friends! I would be most grateful 🙂

All the best for your A levels!

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FRS Chemical Environment

Mr Khemistry

FRS Chemical Environment

FRS Chemical Environment

U and V are structural isomers with molecular formula C7H16.

Both U and V produce the same number of possible structural isomers upon reaction with chlorine to form monochlorinated compounds with the formula C7H15Cl.

Which pairs are possible structures of U and V?

Or

Have a look at the different colour coded hydrogen atoms. Those with the same colour is the same type of hydrogen, i.e. they will form the same product if they are substituted by chlorine. 

Do look out for plane of symmetry as it will greatly accelerate the speed at which you identify FRS Chemical environment.

So answer is 1 and 3 only!

If you’ve enjoyed this organic MCQ, do share it with your friends and see if they are able to do it quickly.

Join us for our weekly tuition classes where we will tackle more of such questions together!

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Free Radical Substitution MCQ Analysis

Mr Khemistry

Free Radical Substitution MCQ

This MCQ is about free radical substitution, be sure to read up before looking at the solution!

Which of the following is a possible product in the reaction between cyclohexane and bromine with UV light?

Free Radical Substitution

Analysis:  The common answer dicyclohexane isn’t one of the given options. So we will have to choose from the above options.

dicyclohexane

 

 

 

 

 

Solution:

A: Note that this option has a total of 14 carbon atoms, not 18. The cyclohexane radicals all has 6 carbon atoms so the products should be in multiples of 6.

B: Similarly, this option has a total of 13 carbon atoms, not 18.

C: This option has 16 carbon atoms.

D: This option has 18 carbon atoms and is the correct answer! Do remember that cyclohexane can undergo multiple abstraction of H atom by the bromine radical.

If you liked this question, share it with your friends and see if they know how to do it! If you need help for organic chemistry, consider signing up for our weekly classes. We have challenging weekly Organic multiple choice questions just like this one for your practice.

Click here for more details!

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